Hints and Tips - Safety Warning

Date: Wed, 26 May 1999
From: C Knight
To:British-Cars Pre-War
Subject: Safety Warning

For the first time in some 35 years messing about with old cars I've just had an SU electric fuel pump diaphragm fail on my MGTA. I noticed an oily drip under the Bakelite end cover. On removal there was petrol inside the cover. I hadn't thought about where the petrol goes if the diaphragm ruptures. If the pump is mounted horizontally, as on my MG, then the petrol goes through the hole in the centre of the coil housing and into the end cover where the contacts are arcing away ready to ignite it. I have not decided what to do apart from fitting a new diaphragm, but contact less switching is a possible.

As a side issue the failed diaphragm, which was about 2 years old, appeared to have dissolved in the petrol leaving bare canvas visible. Anyone had any problems with unsuitable materials on SU diaphragms? I hope nobody has any nasty accidents due to this problem.



From: Robert A. Johnson
To: C Knight
Subject: Re: Safety Warning
Date: Sat, 29 May 1999

By any chance are you using petrol with the additive MTBE such as has been the case here in California? Although I don't know if it has been proven as a fact, it has been rumored to be the cause of softening or dissolving of certain rubber-like compounds in old fuel systems.

The Governor of California has just recently signed a ban on MTBE (as it is getting into the groundwater supply). The ban will be implemented as a phaseout over the next several years. I began my personal phaseout sometime ago and always try to patronize filling stations whose petrol is MTBE-free already.

Bob Johnson
Webmaster at
Early MG Classifieds - http://consultantbob.com/earlymgs/

From: TA Terry
Date: Sat, 29 May 1999
Subject: Re: Safety Warning
To: Bob Johnson, Cliff Knight

Cliff, Bob has a good point....our MTBE will definitely melt some old rubber compounds and the number of car fires in California have increased dramatically since MTBE was introduced. The State has steadfastly denied this but of course those beauratcrats don't get up early enough in the morning to listen to traffic reports in the Bay Area or LA. Finally the drinking water contamination of this crap has cause it to be phased out. There used to be a lot of information on additives on the Chevron web page.

In the UK, there is a lot of panic about the phase out of lead and many additives are being tested or perhaps already added to the gasoline...these may have the side effect of melting old rubber formulations. In general, lead free gasoline is not a problem unless you run high speeds under high load. There is a considerable controversy in New Zealand that lead free gas has increased the cancer rate considerably.

Jerry Felper in LA has made up SU diaphrams that will survived nearly anything. He is on our list.

Good Luck Terry

From: A J Chalmers
Date: Sun, 30 May 1999
Subject: Re: Safety Warning
To: Bob Johnson, Cliff Knight

California also has another problem with petrol - we are running on reformulated stuff that is supposed to cut pollutants. It's side effects are diminished gas mileage, deterioration of gaskets and seals in older cars an significantly higher prices. Ain't progress great?

From:Graham Orme-Bannister
Sent: 04 June 1999
To: british-cars-pre-war

For what it is worth I have asked Burlen Fuel Systems, the "manufacturers of genuine SU.....pumps and components", about the reported problems of diaphragm materials and modern fuels.

They say, without any qualification, "the pump diaphragms we now supply are resistant to modern fuels".

Incidentally I think MTBE is probably a red herring in this context. It is not really an additive but a fuel component; that is, it is directly involved in the combustion process whereas additives are mainly for non combustion purposes such as detergency and corrosion prevention. MTBE (methyl tertiary butyl ether) is an "oxygenate" which adds more oxygen to the combustion process and significantly reduces CO emissions. This is why the environmentalists latched onto it. MTBE is made from methanol, which is more familiar to vintage car (and Indy) racers. MTBE is preferred to alcohols, like methanol and ethanol, because they are less soluble in water and less corrosive to common metals like aluminium. They all have very high natural Research Octane Numbers, around 120. This is why racers like alcohols, and oil companies like oxygenates as blending components.

Graham Orme-Bannister
Alresford, Hampshire, UK

From: Graham Orme-Bannister
Sent: 07 June 1999
To: british-cars-pre-war

Further to my last note on the subject, I have now received the following second message from Burlen Fuel Services which adds flesh to the bones of the last message.

QUOTE: Burlen took over production of SU Fuel Pumps about two years ago and immediately introduced a program of development to ensure the compatibility with modern aggressive fuels. The old three layer diaphragm was replaced by a modern material (American manufacture) using two layers.

There are large stocks (ex military) around the world of old type diaphragms and these are not likely to be modern fuel resistant. To be sure use only genuine SU spares manufactured by Burlen in the last two years.

A further new development by Burlen is our just announced Electronic version - looks the same even sounds the same but it has no points to wear.

Finally, as of 1 June 1999, Burlen are the sole manufacturers of SU Carburetters and Pumps worldwide together with the right to use the SU logo.

J.W.Burnett, Managing Director, Burlen Fuel Systems Limited. UNQUOTE:

I pass this message on without comment. Burlen can be contacted by e-mail at the following address: info@burlen.co.uk

Graham Orme-Bannister Alresford, Hampshire, UK

Webmaster's note: See the Burlen info in suppliers and at www.burlen.co.uk.

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